1. Field of the Invention
The present invention relates generally to probe and sampling devices and more particularly to flexible probe and, sampling devices for use in measuring corrosion levels on trays within fractionating columns used in the petrochemical and refining industries.
2. Brief Description of the Prior Art
Refineries and chemical plants have long experienced problems with corrosion of trays within distillation columns. Corrosion typically occurs at specific temperatures related to the water dew point in the system.
The measurement of the amount of corrosion individual trays are experiencing within a distillation column is of tantamount importance in maintaining the column within optimum operating limits. Tray corrosion can cause a loss of tray efficiency. Ultimately, tray failure may occur resulting in a severe loss of column efficiency.
Electrical resistance probes for measuring corrosion in refinery process equipment have been in use for many years. Heretofore, the probes have been of the straight and rigid type having a basic rodlike structure. These conventional probes as previously used make it difficult if not impossible to access certain areas where corrosion is known to exist. In particular, it is extremely difficult to insert such a probe within a distillation column in a refinery or chemical plant such that the probe can measure corrosion of a specific tray within the distillation column. In order to use such a probe, it is necessary to tap the distillation column above a particular tray on which corrosion is to be measured. The tap must be performed at an angle which converges with the plane of the tray to allow the straight probe to contact the particular tray.
Besides the structural deficiencies of the probes of the prior art, they are also deficient in other respects. Meaningful corrosion measurement is dependent upon accurate temperature measurement and temperature compensation at a place where the corrosion is occurring. It should be recognized that, typically, corrosion measurement probes measure corrosion as a function of electrical resistance and resistance is affected by temperature. The probes heretofore used do not incorporate any rapid temperature compensation in the probe circuitry. Neither do the probes of the prior art have the ability to measure temperature with a thermocouple at the probe extremity.
It is also noted that the probes of the prior art do not incorporate any sampling means. The ability to take a sample of the process fluid at the point where corrosion is being measured is extremely beneficial. It allows the operators to determine precisely what is occurring at that tray level thereby providing precise data upon which to base adjustments to the operating conditions of the distillation column such that further corrosion can be prevented or slowed.